Hybrid Car – More Fun with Less Gas

better mileage with higher octane? - Page 9

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Posted by harry k on January 4, 2007, 2:29 am

Steve wrote:

My understanding (not very good I admit) is that you get nothing for
free.  Seems to me any power produced by flashing to steam has been
from heat stolen from the fuel combustion.  I doubt that there is any
additional power produced by steam.  The basic theory seems to have
been to cool the intake mixture thus getting a denser (and more fuel)
charge into the cyslinder.

Harry K

Posted by Arnold Walker on January 4, 2007, 2:32 pm

Steam expanses more for a given temperature than air.
And with the improved heat expansion and anti-ping control offered by water
You did indeed got more power and the exhaust would be half as hot at the
same time.
In piston engine a 1/3 more and on turbines double the horsepower.You got to
the piston engines were running 50psi boost(22+:1 effective compression
ratio or in otherwords
the compression stroke would heat the air to 900F before you burned any
fuel ) in the air,not automotive turbo pressures.
With the exception of Stubaker ,whose car engines did with a blower on their
sports model.
They did water injection and avgas.....to contol the ping.and like the
aircraft had a switch in the
water tank/pump to kill the ignition advance and blowoff the boost psi, if
the tank ran low.
In both the Stubaker and the plane,if the water switch failed the engine was
trash in seconds
from preignition detonation.But when it worked a Stubaker Commander could
hang with 427 high performance
engines running half the engine displacement.The engine was dropped because
of complex construction ....little did they know that
modern engines now make they look simple ,50years later.

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Posted by clare at snyder.on.ca on January 4, 2007, 5:32 pm


Almost. Getting higher density of the air charge is no problem on a
turbo engine. It is the cooling of the COMBUSTION CHAMBER that was the
challenge - and water injection helped significantly. It DID have the
side effect of acting a bit like an intercooler - but any heat
absorbed in the intake reduced it's primary effect in the cyl.

A higher density intake charge actually INCREASED the tendancy to
detonate by increasing the effective cyl compression - which was part
of the problem in the first place (wouldn't ping without boost)

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Posted by Steve on January 4, 2007, 7:04 pm

harry k wrote:

You're right in that the main gain is getting a denser cooler mixture
into the cylinder, but I think there is a *small* additional gain when
water vapor is present in the combustion chamber because we're not
dealing with ideal gasses. If all the gasses involved were truly ideal,
then you would be correct. In addition, most WWII aircraft engines made
some small use of the jet thrust from the exhaust stacks, and water
certainly adds mass-flow to the engine and would add some jet thrust.
IIRC, I've seen an estimate that a P-51's Merlin engine produces a few
hundred pounds of jet thrust from its exhaust at full power. Not enough
to even move the aircraft on the ground by itself, but certainly enough
to offset the drag of the exhaust system itself sticking out into the
slipstream, and therefore a net benefit.

Posted by clare at snyder.on.ca on January 3, 2007, 9:50 pm


GM did, back in '60 to '63 with the turbo Olds Jetfire and IIRC, the
Turbo Monza Corvair. Don't think it was standard on the Monza, but I
know some did use it (possibly a "dealer add-on" using Olds parts)

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